1. Field of the Invention
This invention relates to a flame retardant, self-extinguishing polymer composition. More particularly, this invention relates to the use of tribromocumene as a flame retardant additive in polymers. A polymer of particular interest is polyurethane.
2. Description of the Prior Art
The problem of the flammability of polymers has received considerable attention. A variety of compounds exist that provide satisfactory flame resistance, smoke suppression and self-extinguishing properties.
The conventional flame retarding agents for polymers fall within two categories. They are either reactive or additive. The reactive compounds are incorporated into the structure or backbone of the polyurethane. Additive flame retardants are only physically incorporated into the polymerized product. Both reactive and additive flame retardant compounds may be present in the same system.
Polyurethanes are one type of polymer that are usually prepared by combining a liquid polyol, such as a polyester, glycol or polyglycol, with a stoichiometric equivalent of a liquid organic polyisocyanate in the presence of a suitable catalyst. Both solid and liquid flame retardant compounds have application in polyurethanes. One solid additive designed for use in flexible polyurethane foam is pentabromoethylbenzene described in U.S. Pat. No. 4,232,085. Other solid flame retardant compounds used in polyurethane compositions are tetrabromoethylcyclohexane and N,N'-1,2-ethane-bis(5,6-dibromonorbornane-2,3-dicarboximide). When trying to incorporate these solid additives into the liquid polyol/liquid polyisocyanate systems it is difficult to prevent the solid flame retardant from volatilizing. The use of a liquid flame retardant in these polyurethane compositions would be advantageous. It has been discovered that tribromocumene, a liquid flame retardant additive with low volatility, is an effective flame retardant in polymer compositions. Since tribromocumene is a liquid it is of special interest in polyurethanes.